85jas
Newbie
Afternoon ladies & gents...
Of course there are plenty of threads discussing widgets / apps to directly monitor battery current draw, such as this and this. I've been using CurrentWidget to log and plot my battery usage and at first glance it does exactly what it says on the tin...
However, being a proper geeky character, this wasn't good enough for me. I noticed that, during standby, CurrentWidget reports my phone is running at ~120mA, a figure which surprised me. So, to test, I imported the data into everyone's favourite spreadsheet package and averaged the current usage over a time period. The results were very curious!
In a ten hour period of partial usage my average battery current was 270mA, therefore I used 2700mAh of charge. Given that the phone has a 1730mAh battery either 1. HTC have created a device which, for the first time in human history, overcomes the first law of thermodynamics or 2. something rum is up with the current reporting. Over this time period my fully charged battery dropped to 30%, indicating by way of battery voltage that 1211mAh had been used - during discharge of currently >1C Li-Ions have a relatively linear capacity/voltage slope (tho temperature dependent), so the assumption at least holds in part...
What is going on? My only explanation is that every time the reporting software generates a log point (every 1 min) the current draw jumps to accommodate this... but the refresh rate of the current draw is only every 30 seconds or so, the system file (/sys/class/power_supply/battery/current_now I think) only gets written to every 30 seconds. So it doesn't seem to be that. Only thing I can think of is some sort of scaling factor must be applied... but that feels wrong.
Let's face it, It's not worth losing sleep over - but I am dead curious! So, to stop me actually directly measuring the battery current with a shunt (will probably happen anyway!) please discuss
Of course there are plenty of threads discussing widgets / apps to directly monitor battery current draw, such as this and this. I've been using CurrentWidget to log and plot my battery usage and at first glance it does exactly what it says on the tin...
However, being a proper geeky character, this wasn't good enough for me. I noticed that, during standby, CurrentWidget reports my phone is running at ~120mA, a figure which surprised me. So, to test, I imported the data into everyone's favourite spreadsheet package and averaged the current usage over a time period. The results were very curious!
In a ten hour period of partial usage my average battery current was 270mA, therefore I used 2700mAh of charge. Given that the phone has a 1730mAh battery either 1. HTC have created a device which, for the first time in human history, overcomes the first law of thermodynamics or 2. something rum is up with the current reporting. Over this time period my fully charged battery dropped to 30%, indicating by way of battery voltage that 1211mAh had been used - during discharge of currently >1C Li-Ions have a relatively linear capacity/voltage slope (tho temperature dependent), so the assumption at least holds in part...
What is going on? My only explanation is that every time the reporting software generates a log point (every 1 min) the current draw jumps to accommodate this... but the refresh rate of the current draw is only every 30 seconds or so, the system file (/sys/class/power_supply/battery/current_now I think) only gets written to every 30 seconds. So it doesn't seem to be that. Only thing I can think of is some sort of scaling factor must be applied... but that feels wrong.
Let's face it, It's not worth losing sleep over - but I am dead curious! So, to stop me actually directly measuring the battery current with a shunt (will probably happen anyway!) please discuss